small fix for Makefile
small fix for Makefile

This fails if for example only hairtunes.c was changed but not alac.c.

hendrikw82/shairport,albertz/shairport,skaman/shairport,mspasov/shairport,IronBeard/shairport,bowlofstew/shairport,hendrikw82/shairport,hendrikw82/shairport,IronBeard/shairport,mspasov/shairport,IronBeard/shairport,dotmpe/shairport,narakai/shairport,dotmpe/shairport,bowlofstew/shairport,narakai/shairport,skaman/shairport,dotmpe/shairport,narakai/shairport,albertz/shairport,bowlofstew/shairport